Gambling becomes dangerous when people continue to chase losses until they become severely addicted, leading to financial ruin and ultimately depression and mental illness.
It's just that when things like depression kick in, it's a very delicate thing for a person. The most delicate cases are those because the person usually can't find a solution, Some commit suicide and believe that's how they'll fix it, I think that when there are very Strong symptoms, help should be immediate You shouldn't think about what to do, but rather act quickly. A life could be saved.
Though what you said is true, in real situation, the victim or the person that's addicted to gambling is not fully aware that he is still in control and won't really see the symptoms until it's too late. Sometimes the person won't really notice it and thus result to depression and suicide, so it's better to have someone to check up on you, or while you are still capable, stop playing and if you really can't stop, then it's time to go see a therapist before it's too late.
Some are unaware, but most probably just don't want to admit it

It's not without reason that addiction can be recognized from the start, but there are still many people with big egos who don't want to admit that they are addicted because they think that addiction is the worst condition and can be a disgrace for gamblers, so they don't want to admit it even though they are aware that they have been exposed to this.
It's possible that some people don't realize they've entered the stage of addiction, but on the other hand, when compared to those who have been aware from the start, I think we know that they know and are aware that their level of gambling is already very high. However, because of their big egos and unwillingness to admit that they are addicted, they prefer to let it go until it reaches a stage that is even worse.